1. Field of the Invention
The present invention relates to an ultrasound diagnosis apparatus and, more particularly, to an ultrasound diagnosis apparatus having a function of analyzing the motion information, blood flow information, and the like of living tissue, an ultrasound image display apparatus, and an ultrasound image display method.
2. Description of the Related Art
An ultrasound diagnosis apparatus emits ultrasound waves generated by ultrasound transducers incorporated in an ultrasound probe into an object to be examined, receives reflected signals originating from acoustic impedance differences in the object tissue through the ultrasound transducers, and displays the resultant image on a monitor.
This diagnosis method allows easy observation of real-time two-dimensional images by simple operation of bringing the ultrasound probe into contact with the body surface, and hence is widely used for functional and morphological diagnoses of organs such as the heart.
In ultrasound diagnosis of tissue such as the heart, in particular, it is very important to objectively and quantitatively evaluate the function of the tissue. The test items in this diagnosis include measurement of the motor function of the heart tissue, the velocity and disturbance of a blood flow, an intracardiac area and volume, and the like.
The M-mode method of repeatedly transmitting and receiving ultrasound waves in a predetermined direction and observing temporal changes in the position of a reflecting region from the resultant reflected signals from the tissue is a test method conventionally used as a technique of quantifying the motion of a cardiac valve or wall or the like.
Conventionally, the M-mode method has been executed on the basis of the locus of luminance on a display window which is determined by the intensity of a reflected signal. Recently, however, with the development of the tissue Doppler method, not only the reflection intensity from an organ such as a cardiac valve or wall but also temporal changes in the movement velocity at the region can be observed. In addition, as disclosed in Jpn. Pat. Appln. KOKAI Publication No. 9-201361, the locus of the movement of an organ can be tracked more accurately from the positional information of a specific region and the movement velocity information of the region which are obtained by the above M-mode method. This has improved the quantification precision of a cardiac function.
In contrast to the conventional M-mode method of displaying temporal changes concerning living tissue in the transmission/reception direction of ultrasound waves, a new M-mode method has been proposed in, for example, Jpn. Pat. Appln. KOKAI Publication Nos. 06-285065 and 10-71147, which extracts biometric information such as a tissue movement velocity in a region along a line segment (LOI (Line of Interest)) set on a two-dimensional image and displays temporal changes in the biometric information by using a display method similar to the conventional M-mode method. In this specification, this new M-mode method (i.e., the M-mode display method associated with an arbitrary LOI which is not limited to the scanning line direction) will be referred to as an “arbitrary M-mode method”. According to this method, a wall motion can be easily evaluated by setting a linear LOI on a cardiac wall, blood vessel wall, or the like.
Each of the above references concerning the arbitrary M-mode method, however, described only a method of generating arbitrary M-mode images and a method of displaying such images, but made no mention of a simple, intuitive quantification method concerning arbitrary M-mode image data. That is, in each of the above conventional techniques, an arbitrary M-mode image is observed, and the intensity and the like of the image are determined by measuring with observer's eyes using a color map and the like. This made it impossible to quantitatively evaluate a physiological characteristic of a patient such as a movement velocity in a specific region. Furthermore, since no consideration is given to the correspondence between a time phase or spatial position on an arbitrary M-mode image and a two-dimensional image displayed on the same display window, it is impossible to check the position of a region to be quantified on the two-dimensional image.